JPH07291775A - Apparatus for growing crystal from solution and method for growing crystal from solution - Google Patents

Abstract

PURPOSE:To obtain a bulky single crystal having a high crystallinity and desired bore by forming an annular difference in level for fixing a seed crystal to a boundary between a part having this seed crystal and a heat sink and a part having a soln. at the time of executing crystal growth by forming a temp. difference above and below a soln., arranging 4 source crystal in the high-temp. part and arranging the seed crystal in the low-temp. part. CONSTITUTION:A horn type quartz crystal tube 1c having a tapered inside surface is connected to the bottom end of a cylindrical quartz tube 1b and a quartz tube 1a is connected to its small bore end. The top end of the tube 1a is provided with the annular difference in level to be fitted with the seed crystal. ZnSe polycrystals are used for the source crystal 4. An alloy formed by mixing Se and Te at a molar ratio 30:70 is used for a soln. 6. After a vessel 1 for crystal growth is evacuated to a high vacuum, this vessel is sealed by quartz caps 9, 10. The vessel is arranged into an electric furnace 12. The vessel 1 is heated up by this electric furnace 12 in a reverse state of Fig. to melt the solvent 6. The vessel is then put into the state of Fig. The crystal is allowed to grow by forming the temp. gradient in such a manner that the part of the crystal 4 attains the high temp.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION This invention relates to crystal growth, and more particularly to solution crystal growth. Solution crystal growth, which can lower the growth temperature, is expected as a bulk crystal growth technique for compound semiconductors with high vapor pressure, particularly II-VI group compound semiconductors.

[0002]

2. Description of the Related Art FIG. 5 shows an example of a conventional solution crystal growth apparatus. A cross section of the crystal growth apparatus is shown on the left side of the figure, and a temperature distribution set in the crystal growth apparatus is shown on the right side in a graph. The crystal growth apparatus comprises a vacuum-grown crystal growth container 1, a heat sink 7 arranged therein, a seed crystal 2, a seed crystal retainer 3, a source crystal 4, and a solvent 6 fixed on the upper surface thereof. ing. This crystal growth container is arranged in the temperature distribution shown in the graph on the right side of the figure.

The source crystal 4 in the high temperature portion dissolves in the solvent 6 up to the saturation solubility in the high temperature portion. The source crystal component dissolved in the solvent 6 also moves to the low temperature part by diffusion, so that the solution in the low temperature part is supersaturated. By contacting the seed crystal 2 with the supersaturated solution, a bulk single crystal grows on the seed crystal 2.

[0004]

In the production of a bulk single crystal using the crystal growth apparatus shown in FIG. 5, the diameter of the columnar grown crystal is smaller than the diameter of the seed crystal 2, and the seed crystal is grown from the grown crystal. It becomes smaller gradually when cut out and repeated growth. Further, it is difficult to obtain a single crystal having a size sufficient for cutting out a wafer having a desired diameter by using a small seed crystal.

An object of the present invention is to provide a crystal growth technique capable of producing a bulk single crystal having a desired diameter and a good crystallinity from a small seed crystal.

[0006]

In the solution crystal growth apparatus of the present invention, a temperature difference is formed above and below the solution, a source crystal is arranged at a high temperature part of the solution, and a seed crystal is arranged at a low temperature part of the solution. In a solution crystal growth apparatus for performing crystal growth, a first space for accommodating a seed crystal and a heat sink and the first space
Second space for accommodating a solution provided so as to be adjacent to the seed crystal contained in the second space, and at least the seed crystal side portion of the second space has a smaller inner diameter on the seed crystal side. Sides are demarcated by the tapered inner wall, and at the boundary between the first space and the second space,
A crystal growth container in which a convex portion for fixing a seed crystal protruding inward from the inner wall is formed, and a shape which is inserted into the first space and is substantially along the inner wall of the first space And a heat sink having.

[0007]

The side of the space above the seed crystal in the crystal growth container has a tapered inner wall whose inner diameter becomes smaller on the seed crystal side, and the crystal is grown on the seed crystal along the inner wall to form the seed crystal. A bulk crystal having a diameter larger than that of the crystal can be obtained.

Further, by forming a convex portion for fixing the seed crystal on the inner wall of the crystal growth container,
The seed crystal can be fixed by being sandwiched between the convex portion and the heat sink. Thereby, the seed crystal can be more stably fixed.

[0009]

EXAMPLES First, a reference example for producing a bulk single crystal having a larger diameter from a small seed crystal will be described.

As shown in FIG. 3, a crystal growth container 1 is prepared in which a small diameter quartz tube 1a and a large diameter quartz tube 1b are connected by a horn type quartz tube 1c having a tapered inner surface. At the beginning, the upper end of the crystal growth container 1 is left open. A heat sink 7 is housed in the small diameter portion 1 a of the crystal growth container 1.

The seed crystal 2 having the same diameter as the heat sink is placed on the upper surface of the heat sink 7 of the crystal growth container thus prepared. Crystal growth container 1 beside the seed crystal 2
Seed crystal 2 by heating the side surface and making it inward
To fix.

Next, after the source crystal 4 and the solvent 6 are charged, the inside of the crystal growth container 1 is evacuated to seal the open end of the upper end. The source crystal 4 is held at a predetermined position by a protrusion or the like provided on the inner surface of the crystal growth container 1.

The crystal growth container 1 thus prepared is placed in a cylindrical heater that heats the internal space by radiant heat, and the temperature distribution shown in the graph on the right side of the drawing is obtained. On the seed crystal 2, the growth crystal 5 grows while gradually increasing the diameter along the tapered inner surface of the quartz tube 1c.

In the reference example shown in FIG. 3, since heat is applied from the side surface of the crystal growth container 1 to fix the seed crystal 2, the seed crystal 2 experiences a thermal history before crystal growth. When the seed crystal 2 is exposed to a high temperature, the crystal component is sublimated and the crystal surface is roughened or the composition is changed. Further, if the sublimated crystal component adheres to the inner surface of the crystal growth container 1, abnormal growth may occur using the crystal component as a growth nucleus. Furthermore, it is difficult to stably and reproducibly fix the seed crystal.

FIG. 4 shows another reference example of the crystal growth apparatus proposed by the inventor of the present application in order to solve these drawbacks.
A large-diameter end of a horn-type quartz tube 1c having a tapered inner surface is connected to the lower end of the cylindrical quartz tube 1b whose upper and lower sides are open. Tapered surface of horn type quartz tube 1c and quartz tube 1b
The angle formed with the central axis of is about 60 °. The small-diameter end of the horn-type quartz tube 1c is composed of a cylindrical side surface having substantially the same diameter as the quartz tube 1b and an upper surface having an opening having substantially the same diameter as the small-diameter end of the horn-type quartz tube 1c, and the lower end is open. Quartz tube 1
a is connected. In the opening on the upper surface of the quartz tube 1a,
An annular step is formed to fit the seed crystal.

The crystal growth container 1 thus formed is etched with hydrofluoric acid to clean the surface. A heat sink 7 having a truncated cone shape having an outer diameter substantially the same as the inner diameter of the quartz tube 1a and an upper end having a diameter substantially equal to the opening diameter of the upper surface of the quartz tube 1a is prepared. A seed crystal 2 having a diameter substantially the same as the opening diameter of the upper surface of the quartz tube 1a is placed on the upper surface of the heat sink 7, and the heat sink 7 and the seed crystal 2 are inserted into the quartz tube 1a from the lower end.

The seed crystal 2 is fitted and fixed in the step formed in the opening on the upper surface of the quartz tube 1a. Quartz tube 1a
The quartz cap 9 is inserted from the lower end of the and sealed. After that, a cylindrical source crystal 4 made of ZnSe polycrystal is inserted into the crystal growth container 1 from the upper open end. The source crystal 4 is fixed by narrowing the quartz tube 1b at the top and bottom. Next, the solvent 6 is charged into the crystal growth container 1 from the upper open end. The upper open end of the crystal growth container 1 is closed with a quartz cap 10, and the inside is evacuated to a vacuum degree higher than 2 × 10 ⁻⁶ Torr and sealed.

The crystal growth container 1 thus prepared is placed in an electric furnace 12 having a vertical heating space. Crystal growth is performed on the seed crystal 2 by forming a temperature gradient such that the seed crystal part has a predetermined crystal growth temperature and the upper part has a higher temperature.

In the crystal growth apparatus shown in FIG. 4, a cavity 11 is formed between the inclined surface of the truncated cone formed on the upper end of the heat sink 7 and the inner surface of the quartz tube 1a. When the solution penetrates into the cavity 11, the seed crystal 2 is arranged at the high temperature part of the solution in the cavity. Then, a phenomenon occurs in which the seed crystal 2 in the high temperature part is dissolved in the solution and is precipitated in the low temperature part in the lower part of the cavity. As a result, the seed crystal 2 disappears and the cavity 1 disappears.
Polycrystal 8 grows at the bottom of 1.

Next, an embodiment of the present invention will be described with reference to FIG. FIG. 1 shows a sectional view of a crystal growth apparatus according to an embodiment of the present invention. The heat sink 7 has a diameter of 8 mm,
It has a cylindrical shape with a length of 100 mm. The inner diameter of the quartz tube 1a is also about 8 mm, and the inner surface is arranged along the outer surface of the heat sink 7. Otherwise, the configuration is similar to that of the other reference example shown in FIG.

The angle between the tapered inner surface of the horn type quartz tube 1c and the central axis of the crystal growth container 1 is about 60 °. As the source crystal 4, a columnar ZnSe polycrystal was used. In the solvent 6, Se and Te were mixed in advance at a molar ratio of 30:70, and ZnS was mixed until the saturation solubility at 950 ° C.
An alloy obtained by melting e and then solidifying was used. The inside of the crystal growth container 1 is evacuated to a vacuum degree higher than 2 × 10 ⁻⁶ Torr.

The crystal growth container 1 thus prepared is placed in a cylindrical electric furnace 12 having a heating space therein. The crystal growth container 1 is tilted together with the electric furnace 12 so that the lower end in which the heat sink 7 is housed is facing up. The angle of inclination is such that the solvent does not contact the seed crystal 2 and the source crystal 4 when the solvent 6 is completely melted. The temperature is raised with the crystal growth container 1 and the electric furnace 12 tilted to form the solvent 6.

After that, as shown in FIG. 1, the crystal growth container 1 and the electric furnace 12 are erected so that the lower end thereof faces downward. The seed crystal 2 and the source crystal 4 come into contact with the solvent 6. A temperature gradient is provided in the electric furnace 12 so that the portion where the seed crystal 2 is arranged is about 950 ° C. and the portion where the source crystal 4 is arranged is about 1000 ° C. The source crystal 4 dissolves to the saturation solubility at that temperature. The dissolved source crystal component diffuses in the solvent and moves to a low temperature part. Since the saturated solubility is low in the low temperature part, the solution becomes a supersaturated solution. Crystal growth occurs on the seed crystal 2 by contacting the seed crystal 2 with a supersaturated solution having an appropriate degree of supersaturation.

In the embodiment shown in FIG. 1, there is no cavity below the seed crystal 2 as shown in FIG. For this reason,
It is possible to prevent the saturated or supersaturated solution in which the seed crystal 2 is dissolved in the solvent from flowing downward.

For another reference example shown in FIG. 4 and the example shown in FIG. 1, the cross section of the grown crystal was observed with a fluorescence microscope, and the thickness of the seed crystal was changed because of the difference in fluorescent color between the seed crystal and the grown crystal. Was measured. In the case of the other reference example of FIG. 4, all the seed crystals having a thickness of 2.4 mm after crystal growth were dissolved. On the other hand, in the case of the example of FIG. 1, the thickness in which the seed crystal was dissolved was 100 μm or less. Thus, FIG.
In the embodiment, the crystal can be grown on the seed crystal without completely dissolving the seed crystal.

FIG. 2 is a sectional view of a crystal growth container according to another embodiment of the present invention. The heat sink 7 has a shape similar to that shown in FIG. 4, and its upper end is formed in a truncated cone shape. The inner surface of the upper part of the quartz tube 1a is formed in a tapered shape so as to follow the side surface of a truncated cone formed on the upper end of the heat sink 7. Otherwise, the configuration is similar to that of the other reference example shown in FIG.

By forming the outer surface of the heat sink 7 and the inner surface of the quartz tube 1a in which the heat sink is housed into substantially the same shape as described above, the crystal growth container is configured so that no cavity is formed below the seed crystal 2. can do. Also in the crystal growth apparatus shown in FIG.
Since the cavity is not formed below, the same effect as the crystal growth apparatus shown in FIG. 1 can be obtained. Since the upper part of the heat sink has a truncated cone shape, the thermal resistance of the lower part of the heat sink can be reduced and a good heat flow can be secured.

In the above embodiment, an example in which ZnSe is grown has been described, but the present invention is not limited to ZnSe and is also applied to growth of a bulk single crystal of II-VI group compound semiconductor having a diameter larger than that of a seed crystal. It is possible.

The present invention has been described above with reference to the embodiments.
The present invention is not limited to these. For example, it will be apparent to those skilled in the art that various modifications, improvements, combinations, and the like can be made.

[0030]

As described above, according to the present invention,
The single crystal can be grown on the seed crystal by suppressing the dissolution of the seed crystal during the crystal growth.

[Brief description of drawings]

FIG. 1 is a sectional view of a crystal growth apparatus according to an embodiment of the present invention.

FIG. 2 is a sectional view of a crystal growth apparatus according to another embodiment of the present invention.

FIG. 3 is a sectional view of a crystal growth apparatus according to a reference example.

FIG. 4 is a cross-sectional view of a crystal growth apparatus according to another reference example.

FIG. 5 is a cross-sectional view of a crystal growth apparatus according to a conventional example and a graph showing a temperature distribution in the crystal growth apparatus.

[Explanation of symbols]

 1 Crystal growth container 2 Seed crystal 3 Seed crystal suppression 4 Source crystal 5 Growth crystal 6 Solvent 7 Heat sink 8 Polycrystal 9, 10 Cap 11 Cavity 12 Electric furnace

Claims (4)

[Claims] 1. A solution crystal growth apparatus for forming a temperature difference above and below a solution, arranging a source crystal at a high temperature part of the solution and arranging a seed crystal at a low temperature part of the solution to perform crystal growth, A first space in which the heat sink is housed,
A second space for accommodating a solution provided adjacent to the seed crystal contained in the first space, wherein at least the seed crystal side portion of the second space has an inner diameter on the seed crystal side. Is defined laterally by a tapered inner wall, and a convex portion for fixing a seed crystal protruding inward from the inner wall is provided at a boundary portion between the first space and the second space. Growth apparatus having a crystal growth container (1) in which a ring-shaped portion is formed and a heat sink (7) inserted into the first space and having a shape substantially along the inner wall of the first space . 2. The solution crystal growth apparatus according to claim 1, wherein the first space has an inner diameter substantially the same as the diameter of the seed crystal. 3. The seed crystal side portion of the first space,
2. The apparatus for growing a solution crystal according to claim 1, wherein the upper end has an inner diameter substantially the same as the diameter of the seed crystal, and the side is defined by a tapered inner wall having a larger inner diameter at the lower end. 4. A solution crystal growth method in which a temperature difference is formed above and below the solution, a source crystal is arranged at a high temperature part of the solution, and a seed crystal is arranged at a low temperature part of the solution to perform crystal growth. A first space in which the heat sink is housed,
A second space for accommodating a solution provided adjacent to the seed crystal contained in the first space, wherein at least the seed crystal side portion of the second space has an inner diameter on the seed crystal side. Is defined laterally by a tapered inner wall, and a convex portion for fixing a seed crystal protruding inward from the inner wall is provided at a boundary portion between the first space and the second space. A crystal growth container in which a ring-shaped portion is formed, a step of preparing a heat sink having a shape substantially along the inner wall of the first space and having a seed crystal mounting surface on the upper surface, and a seed crystal Mounting the seed crystal and the heat sink on the seed crystal mounting surface of the heat sink from the open end of the crystal growth container on the side of the first space into the first space; The convex portion A step of inserting until contacting, a step of sealing the open end of the crystal growth container on the side of the first space, a solvent and a source crystal are put into the second space, and then placed in the crystal growth container. A solution crystal growth method, which comprises a step of forming a predetermined temperature distribution and performing crystal growth.